La <sub> 0.5 </ Sub> Of Mno <sub>, Of Sr <sub> 0.5 </ Sub> 3 </ Sub> Preparation And Characterization Of Perovskite-type Oxides

Perovskite mixed oxides have been raised world-wide concern because of their remarkable ability in the treatment of exhaust. This paper is mainly engaged in two ways to synthesize La0.5Sr0.5MnO3, namely hydrothermal method and co-precipitation method in order to find out which is the appropriate way to prepare the target product. Meanwhile, surfactant PEG-4000 has been adopted to optimize the physical and chemical capabilities of the product. XRD, TG, SEM, BET and H2-TPR have been used for the characterization of the product.The effects of different hydrothermal temperature and calcination conditions on the phase formation of the product prepared by hydrothermal method have been studied. XRD shows that, no single-phased perovskite structured mixed oxides Lao.5Sro.5Mn03 can be obtained through hydrothermal method regardless of the change of experiment conditions. It can be concluded that hydrothermal method is not the appropriate way to synthesize La0.5Sr0.5MnO3.The effects of calcination temperature as well as calcination time on the phase formation of the product prepared by co-precipitation method have also been discussed. The calcination temperature has been identified with XRD and TG analysis. pH value for co-precipitation has been found by calculation as well as experiment. The optimal experimental conditions are:Co-precipitaiton pH:10; calcination temperature:850℃, calcination time:4h. With the increase of the temperature, the specific surface area has been reduced. And the specific surface area of product with single phase has reached by 6.86 m2·g-1.In order to study the effects of PEG-4000 on the physical and chemical capabilities of La0.5Sr0.5MnO3, a series of experiments have been designed. XRD results show that all the products obtained are single-phase and the amount of the dispersant has no effect on the phase formation. BET results show that PEG-4000 plays an important role in the specific surface area and the catalytic capabilities of the product. The appropriate amount of the dispersant can be beneficial for the specific surface area of the product, and remarkably improve its oxidizing capability. SEM results show that PEG-4000 is able to alleviate the agglomeration of the particles and reduce the effects of temperature on the particle agglomeration. H2-TPR show that, the product prepared with PEG-4000 has better oxidizing capability under low temperature and a higher structural stability under high temperature.